Circuit interrupter



APlil. 28,1936 K l J. H. SHULER 2,039,036

CIRCUIT 'INTERRUPTER Min/55555- A -W/T/Va'ssaish ,April .23, l936- f J. H. SHUI- ER 2,039,036-` CIRCUIT INTERRUPTER Filed Jan. 2s, 1934' s sheets-,snaai s.

www V [NSI/mwa INVENTOR g@ Jah/4520@ Patented Apr. 2s, 1936 4PATENT oFFlcE CIRCUIT INTERBUPTER, John H. Shuler, Lexington, Ohio, assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application January z3, 1934, serial No. 707,908

14 Claims'.

My invention relates generally to electro-responsive devices for actuating electrical apparatus, and relates particularly to trip devices for circuit breakers of the type used in controlling distribution feeder and moderate power indus-H trial circuits.

Circuit breakers of this type are usually subjected to very severe and'very exacting operating requirements. 'I'he available power in the supply circuits is frequently extremely large, as

- compared with the normal rating of the device.

This results in very large magnitude short-circuit currents which must be interrupted in very short periods of time in order to prevent damage to the` pro-tected equipment. And despite this necessity for rapid operation upon the occurrence of short-circuit conditions, the breakers must remain closed for a considerable time following the occurrence of moderate overloads, in order to prevent needless and annoying discontinuities of service.

T'he securing of this desired selective operation is entirely a function of the circuit breaker trip device, and heretofore various complicated structures have been in general use. Some of these have utilized a combined thermally-responsive and magnetically-responsive trip element. Others have combined thermally responsive and `magnetically-responsive devices simultaneously actuable to prevent injury tothe current-carrying portions thereof upon the occurrence of overlcads or short-circuit conditions. All of the previously known devices have been expensive to manufacture, most of them including a considerable number of moving parts, any one of which might get out of adjustment and thereby destroy the calibration of the apparatus, and none has been entirely satisfactory.

-It therefore, an object' of my invention to provide an improved electro-responsive device for use with electrical apparatus that shall be more economical to manufacture, and more accurate and reliable in operation than the previously known devices cf this type.

Another object of my invention is to provide an improved current-carrying thermally-responsive device that shall possess suihcient thermal capacity to withstand heavy overload and shortcircuit currents, and which shall at the same time ,he op;Y le to actua-te the associated apparatus upon the i'low therethrough of predetermined lof.: magnitude currents.

A further object of my invention is to provide Sniprcwed vcircuit breaker trip device that sli-l accurately distinguish between overloads and .trt-circuit conditions, and that-shall not readily loose its' calibration.

A still further object of my invention is to provh; .n iliproved, unitary, circuit breaker trip dence that shall include a bimetallic element,`

(Cl. 20G-122) a heater, and means for controlling the rate of heat transfer therebetween. e

/An ancillary object of my invention is to provide an improved electro-responsive device, according to the above objects of my invention, that shall be readily removable asa unit from the associated apparatus to permit the substitution therefor of other similar devices in 'order to alter the rating of the associated apparatus.

Since the principal eld for immediate application of my invention is in connection with circuit breakers for moderate power installations, I shall hereinafter describe an embodiment of my invention as applied to such devices, without, however, in any/way intending to restrict the scope of my invention, except as indicated in the appended claims.

Referring to the drawings: Figure 1 is a plan view of a two-pole, double break circuit breaker embodying the principal elements of my invention. The breaker is shown in the normal open circuit position, and a considerable portion of the cover \has been cutaway in 'order to more fully illustrate the structural features involved; n

Fig. 2 is a plan view similar to Fig. 1 showing the circuit breaker in the closed circuit position; Fig. 3 is a plan view similar to Figs. 1 and 2 showing the circuit breaker in the tripped position;

Fig. 4 is an enlargeddetail view of the removable trip device used in the circuit breaker shown in Figs. 1, 2, and 3;

Fig. 5 is a perspective view of thel trip device shown in Fig. 4; f A I Fig. 6` is `a detail view, partly in section, of the *moving contacts and thesupport member therefor;

Fig.' 7 is an exploded perspective viewof the ing material upon which the various structural features of the device are mounted, a pair of stationary contact assemblages 3 and 5, four terminalsA l, 8, 9, and I0, a pair of moving contacts II and I3 for cooperating with the stationary contact assemblages to open and close the circuit, an operating mechanism I5 for moving the contacts to the open and closed circuit positions, and a trip device Il for causing the operating mechanism I5 to open the circuit upon the occurrence of predetermined conditions. Four upstanding side portions I9 are molded integral with the base I and serve to provide the sides oi the circuit breaker closure. A cover 2| also of molded insulating material is provided for cooperating with the side portions I9 to substantially completely enclose the operating portions of the breaker.

Each of the stationary contact assemblages 3 and 5 includes a exible contact portion 23 and a flexible contact portion 3| (Fig. 8) for engaging the cooperating moving contact. The contact portions 23 are mounted upon an upstanding member 25, molded integral with the base I, by suitable screws 21. These screws 21 also serve to position the two terminals 1 and 8, and to electrically connect those terminals with the contact portions 23. Each of the terminals 1 and 8 has a threaded opening therein (not shown) for engaging one of the screws 29 which are used to connect the line conductors to the breaker.

The second pair of flexible contact portions 3| is positioned closely adjacent the base of the breaker, and each of the flexible contact portions 3| terminates in a flat conducting strip 33 fastened to the base I by a screw 34. The upper conducting strip 33 is electrically connected by suitable means (not shown) to the terminal I0. The lower conducting strip 33 is electrically connected to a cylindrical member 35 molded integral with one o! the side portions I9 (Fig. 8) by means of a screw 31. This cylindrical member 35 is used for electrically connecting the trip device I1 in series with one of the poles of the breaker and is provided with a. threaded opening 4| therein for engaging one of the support screws 43 for the trip device.

A second cylindrical member 45 of conducting material, likewise molded in the side portions I9 of the breaker closure, is provided for engaging the other terminal of the trip device I1. The interior or this cylindrical conducting member is likewise threaded for receiving the other support screw 43. The lower end of thecylindrical conducting member -45 is connected to the terminal 9 of the breaker by means or a suitable conducting strip 41 which engages the screw 49 holding theterminal 9 in position on the base of the circuit breaker.

The electrical circuit through each of the poles of the breaker is comparatively direct: Beginning with terminal 1 the current flows successively through the flexible contact portion 23 of the stationary contact assemblage 3 thence through the cooperating movable contact II to the other flexible contact portion 3| of stationary contact assemblage 3, through the conducting strip 33 associated with the` contact portion 3|, and suitable conducting means (not illustrated) to the terminal I0. For the other pole, the current flows successively through the terminal 8, the upper flexible contact portion 23 oi the stationary contact assemblage 5, the moving contact I3, the lower ilexlble contact portion 3| and the associated strip 33, the cylindrical conducting member 35, the terminal 5I of the trip device I1, and thence through the trip device l1, the cylindrical conducting member 45, the strip 41 and the screw 49 to the other terminal 9 of the breaker.

The moving contacts and I3, as -is shown particularly in Fig. 6, are mounted upon a support member 53 which is adapted to pivotally engage the cradle member 55 of the operating mechanism I5 at the point 55. Each of the moving contacts comprises a pair of cylindrical members 51 and 59 of conducting material. Each of the members 51 is provided with a threaded portion EI for engaging a threaded opening 63 in each of the members 59. An insulating plate 65 is interposed between each of the cylindrical members and the support member 53, and these insulating plates 55 in combination with an insulating washer 51 serve to insulate each of the two moving contacts from each other and from the support member.

The operating mechanism includes a frame G9 (see Fig. 9) which is rigidly afiixed to the base I of the circuit breaker by means of suitable screws 10 which engage the threaded openings 1| therein, a bifurcated operating member 13 adapted to be pivotally supportedupon two portions 15 which project outwardly from the frame 69, an overcenter spring 11 for operatively connecting the support member 53 for the moving contacts with the operating member 13, and the movable cradle 55 (Fig. l0) which is provided with a pair of notched portions 19 for engaging and pivotally supporting the support member 53 for the moving contacts. The cradle 55 is pivotally supported upon the frame |59 by means of a pin 8| and is provided with a roller 83 for engaging the projecting latch 85 which forms a part of the trip device I1. The operating member 13 is provided with -a handle portion 81 disposed without the circuit breaker closure, in order to permit manual operation of the mechanism.

The trip device is shovm particularly in Figs. 4, 5, and 7, and includes a frame 9| of conducting material which serves to supportthe several elements of the device and which has the terminal l 5| formed' integral therewith. A pair of bimetallic strips 93 having a length several times their width are fastened to the frame 9| by means of suitable rivets 95. The lower end of the lefthand bimetallic strip 93 (see Fig. 7) is electrically connected to the frame 9|. 'Ihe lower end of the other bimetallic strip 93, however, is insu'- lated from the frame 9| by means of a piece of mica .91 interposed therebetween. The other terminal 99 of the trip device is electricallhY connected to the lower end of the right-hand bimetallic member 93. The upper ends of the two bimetallic strips are mechanically connected by means of a pair of plates |0| of insulating material, a retaining plate |03, a latch plate |05, and two rivets |01 which engage suitable holes in the several members. The latch plate |05 is insulated from the two bimetallic strips 93 by one of theinsulating plates II'II, and the spacing of the holes is such that two ends of the bimetallic strips 93 are insulated from each other.

The electrical circuit through the trip device I1 is completed by means of a looped heater |99, one end of which is electrically connected to each of the bimetallic strips 93 by means of a rivet adapted to extend through suitable openings disposed therein. As shown particularly in Figs. 4 and 7, the heater |09 comprises a plurality of substantially flat looped portions which are disposed in a plane spaced some distance from the plane of the bimetallic strips themselves. It will also be noted that an insulating plate |I3, preierably of mica, is interposed between the iiat portion of the heater and the adjacent surfaces of the bimetallic strips 93. This insulating member I3 in combination with the spacing of the heater serves to reduce the rate of heat transfer betweenthe heater and the thermally-responsive bimetallic strips in order to increase the time delay of the trip device when moderate overload currrents flow therethrough.

the roller 03 forming the part of cradle 55, as is shown particularly in Figs. 2 and 4. The bimetallic strips 93 are so positioned that upon heating they both. tend to move the latch plate |05 in a direction away from the operating mechanism "I5, and when this movement progresses a sufeient distance to cause the latch 85 to release the roller 83, the operating mechanism automatically opens the breaker. v

From the foregoing description, it will be seen that the trip device II comprises a pair of bimetallic elements 93, each of which has a currentcarrying portion, and a heater |09, which is entirely supported upon the bimetallic elements, and which is in series with and connects the two current-carrying portions thereof. The electrical resistance and the thermal capacity of the bimetallic .elements 93 are so proportioned that the ow of large magnitude currents through the current-carrying portions of the bimetallic strips produces sufficient internal heating to cause the actuation of the trip device after a very short cuitJ position in Fig. 1.

interval of time. The thermal capacities and the resistances of the current-carrying paths areso proportioned, however, that the continued ow of moderate over-load currents through the bimetallic elements themselves would be incapable of causing the actuation of the trip device. This inability results from the high thermal capacity of the bimetallic elements, which is necessary in order to prevent any injury to the calibration of the device following the iiow therethrough of large magnitude currents.

The inability of the trip device I1 to function when low magnitude currents flow therethrough necessitates the provision of the separate heater |09. The resistance of this heater and itsv thermal capacity are such that the continued iiow of moderate overloadcurrents therethrough will produce sufiicient heating to cause the operation of the trip device in substantially the same manner as that resulting from the flow of large over-load currents through the bimetallic elements themselves. I have found that the time delay may be very readily and very accurately controlled by adjusting the spacing between the heater |09 and the bimetallic strips 93 themselves and also by inserting a piece of insulating material, such as the mica plate II 3 in that space. The ccmbination of these structural features results in a trip device which is almost instantaneously operable to cause opening of the circuit upon the occurrence of a short-circuit or a very heavy overload condition, and which at the same time will not cause the opening of the controlled circuit upon the occurrence of a moderate over-load con'- dition, until that condition has persisted for a considerable period of time. Moreover, thisimproved arrangement permits the utilization of current-carrying bimetallic elements, having sufiicient thermal capacity to withstand, without injury,- the ilow therethrough of heavy over-load -currentin trip devices operable to cause opening of the associated breaker upon the occurrence of moderate overloads.

The circuit breaker is shown in the open cir- To close the contacts manually the handle 81 of the operating member '13 is moved to the right. This movement brings the moving contacts I I and I3, and causes those contacts to move to the closed circuit position withl a snap action. Both of the poles of the breaker are closed at substantially the same instant. The closed circuit position is shown in Fig. 2, and it will be noted that the reaction forces of the over-center spring I'I which are transmitted through the contact support member 53 tend to bias the cradle 55 in a counter-clockwise direction about the cradle pivot pin 8 I. This biasing force is opposed by the latch portion 85 of the trip device II. l

To open the contacts manually, the operatin handle 81 is moved from the position shown in Fig. 2 to the position shown in Fig. 1. The lirle of action of the over-center spring 11 is brought to the left of Vthe pivot point 56 of the support member 53 for the -moving contacts, and the opening operation takes place with a snap action in substantially the same manner as the closing operation.

When the circuit breakeris in the closed circuit position, and an over-load of suilicient magnitude and duration to cause actuation of the trip device II occurs, the bimetallic strips 93 move so as' to cause the latch 85 to disengage the cradle roller 88. The cradle 55'is then free to move in 'a counter-clockwise direction, and in so moving brings the pivot point 56 of the support member 58 for the moving contacts to the right of the line o! action of the operating spring TI. 'I'he operating spring then moves Fig. 3. In this position, the projecting portion IIS of the cradle, which supports the' roller 83, engages the member Il] which is molded in the base I, thereby deilning the limits of motionof the cradle. The positioning of the pivot points of the other elements of the operating mechanism I5 is such that the handle 81 moves to the central position, thereby indicating that the circuit has been opened due to the operation of the trip device I'I.

In order to restore the various elements of the operating mechanism I5 to an operative condition -following the actuation of the trip device I1, itis merely necessary to move the operating handle 8'I to the normal open circuit posi- This movement of thev tion to a position where the roller 83' re-engagcs y the latch 85 forming a part of the trip device. The breaker may then be manually moved to the closed circuit position in exactly the same manner as described above.

As has been pointed out in a previous paragraph, the trip device is entirely supported from the frame member 9|, which also serves as one of the terminals of the device. The other terminal 09, while it is insulated from the frame member, is rigidly ailixed thereto. Thus the removal of the two screws 43, which .serve to connect the trip device I 'I in the electrical circuit of the breaker, also permits the trip device I1 to be entirely removed as a unit from the breaker closure. This arrangement is of great value in permitting the rating of the breaker to be changed through the subsitution of a similarly proportioned device having a diierent current rating. Moreover, since the single heater |09 for both of the bimetallic elements 83 is mounted thereon, the removal of the trip device also serves to remove the heater. Y

I have shown a trip device in the circuit of only one of the poles of the breaker. It is possible, however, and within the ,province of my invention, that a trip device may be used in both poles with equally satisfactory results.

From the foregoing it will be seen that I have disclosed a new, improved, electro-responsive device which is particularly suitable for use as a circuit breaker trip device. My improved electro-responsive device is simple in design and may be economically manufactured. It is capable of causing the actuation of apparatus used therewith almost immediately following the occurrence of heavy over-load or short-circuit conditions, without any change in the calibration or any injury to the current-carrying parts thereof, and-at the same time, my improved device is capable of causing the actuation of the associated apparatus upon the persistence of moderate over-loads in the connected circuit.

In addition to the above features which are applicable to electrical apparatus generally, I have shown hcw an improved electro-responsive device according to the objects of my invention may be embodied into a removable unitary structure which is readily interchangeable with other devices of a similar character. I have also disclosed certain particular detailed structural arrangements which permit the controlling of the time -delay in the operation of electro-responsive devices, and various other preferred arrangements which are of value in carrying out the objects of my invention.

While in accordance with the patent statutes I have desclosed the foregoing details of a practical embodiment of my invention, it is to be understood that many of these details are merely illustrative, and that variations in their precise form will be both necessary and desirable in certain applications. I desire, therefore, that the language of the accompanying claims shall be limited only by what is explicitly stated therein and by the prior art.

I claim as my invention:

l. 4In electrical apparatus, an electro-responsive device including. a iiat strip of bimetallic material, means for connecting at least a portion of said strip into an electrical circuit, a heater connected in current-responsive relationship with said flat strip, said heater comprising a means of conducting material having a sbstantially flat looped portion, and means for supporting said heater on said strip, said support means including means for positioning the looped portion of said heater in a planethat is substantially parallel to the plane of said strip and is spaced a substantial distance therefrom.

2. In electrical apparatus, an electro-responsive device including a flat strip of bimetallic material having a length several times its width, means for connecting at least a portion of said strip into an electrical circuit, a heater connected in current-responsive relationship with said strip, said heater comprising a means of conducting material having. at least one substantially U-shaped loop therein, and means for supporting said heater on said strip, said support meansjncluding ,means for positioning the side portions of said U-shaped loop in a plane which is disposed a substantial distance from the plane of said strip and which is substan- -tially parallel therewith.

may be lxedly supported adjacent one end thereof, the other end ofsaid strips being movable to effect the operation of said device,` insulating means for mechanically interconnecting said movable ends, Ameans for `connecting at least a portion of each of said strips into an electric circuit, a single unitary heater for both of said strips, electrically connected in series therewith, said heater including a conducting means having a plurality of loops formed therein, and means for supporting said heater on said strips, said support means positioning at least one of said plurality of loops in a plane substantially parallel to the plane of each of said strips.

4. An electro-responsive device for use with electrical apparatus comprising a pair ci ilat strips of bimetallic material, each of which has a length several times its width, means whereby said strips may be iixedly supported adjacent one end thereof, the other end of each of said strips being movable in the same direction to eiect the operation of said device, insulating means for mechanically interconnecting said movable ends, means for connecting at least a portion of each or said strips into an electric circuit, a single unitary heater for both of said strips, electrically connected in series therewith, said heater including a conducting means having a plurality of loops formed therein, and means for mechanically and electrically connecting one end of said heater to each of said strips adjacent the movable end thereof, in order that said heater shall be entirely supported upon said strips, said connecting means being `so arranged that said loops are positioned generally in a plane substantially parallel to the plane of said strips.

5. In electrical apparatus, an electro-responsive device comprising a pair of flat strips of bimetallic material, each 'of said strips having a portion that is movable in the same direction during the operation of said apparatus, insulating means for mechanically interconnecting said movable portions, means for connecting at least a portion of each of said strips into an electrical circuit, and a current-carrying heater connected in electro-responsive relationship with said current-carrying portions and spaced some distance from said strips in order to decrease the rate of heat transfer therebetween. l

6. In electrical apparatus, means for actuating said apparatus, and an electro-responsive device for controlling the operation of said means,.said device including a pair of flat strips of bimetallic material, insulating means for mechanically connecting said strips at one end thereof, means, supported on said connecting means, for operatively engaging said apparatus, means for connecting at least a portion of each 0I said strips into an electrical circuit, and a single current-carrying heater for said strips, said heater being connected in series with said current-carrying portions, and being spaced some distance from said strips in order to decrease the rate of heat transfer therebetween.

'7. In electrical apparatus, means for actuating said apparatus, and an electro-responsive device for controlling the operation thereof, said device including a pair of flat strips of bimetallic material, insulating means for mechanically connecting said strips at one end thereof, means sup ported on said connecting means, for operatively engagingsaid means for actuating said apparatus, means for connecting at least a portion of each of said strips into an electrical circuit, a

. single unitary heater for both of said strips, and

.means, supported on said connecting means, for

cooperating with said means, for actuating said aparatus, means connecting4 at leasta portion of each of said strips into an electrical circuit, a current-carrying heater connected in series with said current-carrying portions and spaced some Adistance from said strips, and a sheet of an insulating material that is not aifected by high temperature .disposed in the space between said heater and said strips for decreasing the rate of heat transfer therebetween.

9. In anelectro-responsive device a pair of l at strips of bimetallic material, means whereby each of said strips may be supported at one end thereof, the other end of each of said strips being movable during the operation of said device, insulating means for mechanically interconnecting said movable ends, means for connecting at least a portion ofeach of said strips into an electrical circuit, a current-carrying heater connected in series with said current-carrying portions of said strips, and means for entirely supporting said heater on said strip, the support means for said strip including means for making possible the removal of said strips and said heater as a unit from said apparatus.

10. In a circuit interrupter, a base, separable contacts and an actuating means therefor xedly mounted on said base, and a removable, currentcarrying trip device operable upon the occurrence of predetermined conditions to effect the operation of said actuating means, thereby causing said separable contacts to be moved to the open circuit position, said trip device including a pair of rigid terminal members which are adapted to engage said base member and uponwhich the other elements of said trip device are supported, insulating means for mechanically interconnecting said terminal members to impart greater rigidity to said tripdevice, and a currentcarrying, electro-responsive means electrically connected across said terminals.

11. In a circuit interrupter, a base, separable contacts and an actuating means therefor iixedly `mounted on said base, and a removable, currentcarrying trip device operable upon the occurrence of predetermined conditions to eiect the operation of said actuating means, thereby causing said separable contacts to be'moved to the open circuit position, said trip device including a pair of rigid terminal members which are adapted to engage said base member and upon which the other elements of said trip device are supported, insulating means for mechanically interconnecting said terminal members to impart greater rigidity .o said trip device, a pair of flat strips of bimetallic material, means for connecting at least a portion of each of said strips into the electrical circuit through said current-carrying trip device, and a singleheater means for v both of said stripsk A a pair of at strips of bimetallic material, each of said strips having a portion which is movable in the same direction during the operation of said apparatus, means for mechanically interconnecting said movable portions, a single current-carrying heater means for said strips, and means for entirely supporting said heater on said strips.

13. In electrical apparatus, means for actuating said apparatus. and an electro-responsive device for controlling the operation of said actuat- 4ing means, said device including a pair of ilat strips of bimetallic material, each of said strips having a portion that is movable during the operation of said device, insulating means for mechanically interconnecting said movable portions, means for connecting at least a portion of each of saidstrips into an electrical circuit, and a current carrying heater connected in electroresponsive relationship with said current carrying portions and being spaced some distance from said strips of bimetallic material, the electrical resistance and the thermal characteristics 4of said bimetallic members being such that' the operation of saidelectro-responsive device is effected when a current of predetermined magnitude iiows through said device for a predetermined time, and the electrical resistance of said heater and the spacing between said heater and said members of bimetallic material being such that the operation of said electro-responsive device ls also effected when a current oi' different predetermined magnitude ilows therethrough for a different predetermined period of time.

14. In electrical apparatus, means for actuat-- ing said apparatus, and an electro-responsive device for controlling the operation of said means, said device including a pair of ilat strips of bimetallic material, each of said strips having a portion that is movable in the same direction during the operation of said device, insulating means `for mechanically interconnecting said movable portions, means for connecting at least a portion of each of said strips into an electrical circuit, and a current carrying heater connected in the electro-responsive relationship with said current carrying portions and being spacedl some dist-ance from said strips in order to decreasethe rate of heat transfer therebetween, the electrical resistance and the thermal characteristics of said bimetallic members being such that the operation of said electro-responsive device is ei'- fected when a current of predeterminedmagnitude iiows therethrough for a predetermined time, and the electrical resistance of said heater and the spacing between said heater and said members of bimetallic material being such that the operation oi' said electro-responsive device is 

